Which one of the following programs contains a syntax error?

Which one of the following programs contains a syntax error?
A . proc sql;
select product.*, cost.unitcost, sales.quantity
from product p, cost c, sales s
where p.item = c.item and
p.item = s.item;
quit;
B . proc sql;
select product.*, cost.unitcost, sales.quantity
from product, cost, sales
where product.item = cost.item and
product.item = sales.item;
quit;
C . proc sql;
select p.*, c.unitcost, s.quantity
from product as p, cost as c, sales as s
where p.item = c.item and
p.item = s.item;
quit;
D . proc sql;
select p.*, c.unitcost, s.quantity
from product, cost, sales
where product.item = cost.item and
product.item = sales.item;
quit;